X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=0cd868ade28b70e40163bbb3ddfca44f0e536b8c;hp=0af212de9c625c3aae3856d6d49e39098302e0f0;hb=cac2e345596b2743053c0285280b81794b3aaf10;hpb=05b9640022d25a75923cc7809409914491a5f9da
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-udev - userspace device management
-
-For more information see the files in the docs/ directory.
-
-Important Note:
- Integrating udev in the system has complex dependencies and differs from distro
- to distro. All major distros depend on udev these days and the system may not
- work without a properly installed version. The upstream udev project does not
- recommend to replace a distro's udev installation with the upstream version.
-
-Requirements:
- - Version 2.6.18 of the Linux kernel for reliable operation of this release of
- udev. The kernel may have a requirement on udev too, see Documentation/Changes
- in the kernel source tree for the actual dependency.
-
- - The kernel must have sysfs, unix domain sockets and networking enabled.
- (unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
- but it does not make any sense - don't complain if anything goes wrong.)
-
- - The proc filesystem must be mounted on /proc, the sysfs filesystem must
- be mounted at /sys. No other locations are supported by udev.
-
-
-Operation:
- Udev creates and removes device nodes in /dev, based on events the kernel
- sends out on device discovery or removal.
-
- - Very early in the boot process, the /dev directory should get a 'tmpfs'
- filesystem mounted, which is populated from scratch by udev. Created nodes
- or changed permissions will not survive a reboot, which is intentional.
-
- - The content of /lib/udev/devices directory which contains the nodes,
- symlinks and directories, which are always expected to be in /dev, should
- be copied over to the tmpfs mounted /dev, to provide the required nodes
- to initialize udev and continue booting.
-
- - The old hotplug helper /sbin/hotplug should be disabled on bootup, before
- actions like loading kernel modules are taken, which may cause a lot of
- events.
-
- - The udevd daemon must be started on bootup to receive netlink uevents
- from the kernel driver core.
-
- - All kernel events are matched against a set of specified rules in
- /lib/udev/rules.d/ which make it possible to hook into the event
- processing to load required kernel modules and setup devices. For all
- devices the kernel exports a major/minor number, udev will create a
- device node with the default kernel name, or the one specified by a
- matching udev rule.
-
-
-Compile Options:
- DESTDIR
- Prefix of install target, used for package building.
- USE_LOG
- If set to 'true', udev is able to pass errors or debug information
- to syslog. This is very useful to see what udev is doing or not doing.
- It is enabled by default, don't expect any useful answer, if you
- need to hunt a bug, but you can't enable syslog.
- DEBUG
- If set to 'true', very verbose debugging messages will be compiled
- into the udev binaries. The actual level of debugging is specified
- in the udev config file.
- USE_SELINUX
- If set to 'true', udev will be built with SELinux support
- enabled. This is disabled by default.
- EXTRAS
- list of helper programs in extras/ to build.
- make EXTRAS="extras/cdrom_id extras/scsi_id extras/volume_id"
-
-
-Installation:
- - The install target intalls the udev binaries in the default locations,
- All binaries will be installed in /lib/udev or /sbin.
-
- - The default location for scripts and binaries that are called from
- rules is /lib/udev. Other packages who install udev rules, may use
- that directory too.
-
- - It is recommended to use the /lib/udev/devices/ directory to place
- device nodes and symlinks in, which are copied to /dev at every boot.
- That way, nodes for broken subsystems or devices which can't be
- detected automatically by the kernel, will always be available.
-
- - Default udev rules and persistent device naming rules are required by other
- software that depends on the data udev collects from the devices,
- and should be installed by default with every udev installation.
-
-Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
- linux-hotplug@vger.kernel.org
+Elogind User, Seat and Session Manager
+Introduction
+------------
+
+Elogind is the systemd project's "logind", extracted out to be a
+standalone daemon. It integrates with PAM to know the set of users
+that are logged in to a system and whether they are logged in
+graphically, on the console, or remotely. Elogind exposes this
+information via the standard org.freedesktop.login1 D-Bus interface,
+as well as through the file system using systemd's standard
+/run/systemd layout. Elogind also provides "libelogind", which is a
+subset of the facilities offered by "libsystemd". There is a
+"libelogind.pc" pkg-config file as well.
+
+All of the credit for elogind should go to the systemd developers.
+For more on systemd, see
+http://www.freedesktop.org/wiki/Software/systemd. All of the blame
+should go to Andy Wingo, who extracted elogind from systemd.
+
+Contributing
+------------
+
+Elogind was branched from systemd version 219, and preserves the git
+history of the systemd project. The version of elogind is the
+upstream systemd version, followed by the patchlevel of elogind. For
+example version 219.12 is the twelfth elogind release, which aims to
+provide a subset of the interfaces of systemd 219.
+
+To contribute to elogind, fork the current source code from github:
+
+ https://github.com/elogind/elogind
+
+Send a pull request for the changes you like.
+
+To chat about elogind:
+
+ #guix on irc.freenode.org
+
+Finally, bug reports:
+
+ https://github.com/elogind/elogind/issues
+
+Why bother?
+-----------
+
+Elogind has been developed for use in GuixSD, the OS distribution of
+GNU Guix. See http://gnu.org/s/guix for more on Guix. GuixSD uses a
+specific init manager (DMD), for reasons that are not relevant here,
+but still aims to eventually be a full-featured distribution that can
+run GNOME and other desktop environments. However, to run GNOME these
+days means that you need to have support for the login1 D-Bus
+interface, which is currently only provided by systemd. That is the
+origin of this project: to take the excellent logind functionality
+from systemd and provide it as a standalone package.
+
+We like systemd. We realize that there are people out there that hate
+it. You're welcome to use elogind for whatever purpose you like --
+as-is, or as a jumping-off point for other things -- but please don't
+use it as part of some anti-systemd vendetta. Systemd hackers are
+smart folks that are trying to solve interesting problems on the free
+desktop, and their large adoption is largely because they solve
+problems that users and developers of user-focused applications care
+about. We are appreciative of their logind effort and think that
+everyone deserves to run it if they like, even if they use a different
+PID 1.
+
+Differences relative to systemd
+-------------------------------
+
+The pkg-config file is called libelogind, not libsystemd or
+libsystemd-logind.
+
+The headers are in , so like instead
+of .
+
+Libelogind just implements login-related functionality. It also
+provides the sd-bus API.
+
+Unlike systemd, whose logind arranges to manage resources for user
+sessions via RPC calls to systemd, in elogind there is no systemd so
+there is no global cgroup-based resource management. This has a few
+implications:
+
+ * Elogind does not create "slices" for users. Elogind will not
+ record that users are associated with slices.
+
+ * The /run/systemd/slices directory will always be empty.
+
+ * Elogind does not have the concept of a "scope", internally, as
+ it's the same as a session. Any API that refers to scopes will
+ always return an error code.
+
+On the other hand, elogind does use a similar strategy to systemd in
+that it places processes in a private cgroup for organizational
+purposes, without installing any controllers (see
+http://0pointer.de/blog/projects/cgroups-vs-cgroups.html). This
+allows elogind to map arbitrary processes to sessions, even if the
+process does the usual double-fork to be reparented to PID 1.
+
+Elogind does not manage virtual terminals.
+
+Elogind does monitor power button and the lid switch, like systemd,
+but instead of doing RPC to systemd to suspend, poweroff, or restart
+the machine, elogind just does this directly. For suspend, hibernate,
+and hybrid-sleep, elogind uses the same code as systemd-sleep.
+Instead of using a separate sleep.conf file to configure the sleep
+behavior, this is included in the [Sleep] section of
+/etc/elogind/login.conf. See the example login.conf for more. For
+shutdown, reboot, and kexec, elogind shells out to "halt", "reboot",
+and "kexec" binaries.
+
+The loginctl command has the poweroff, reboot, sleep, hibernate, and
+hybrid-sleep commands from systemd, as well as the --ignore-inhibitors
+flag.
+
+The PAM module is called pam_elogind.so, not pam_systemd.so.
+
+Elogind and the running cgroup controller
+-----------------------------------------
+While 'configure' runs, it will detect which controller is in place.
+If no controller is in place, configure will determine, that elogind
+should be its own controller, which will be a very limited one.
+
+This approach should generally work, but if you just have no cgroup
+controller in place, yet, or if you are currently switching to
+another one, this approach will fail.
+
+In this case you can do one of the two following things:
+
+ 1) Boot your system with the target init system and cgroup
+ controller, before configuring and building elogind, or
+ 2) Use the --with-cgroup-controller=name option.
+
+Example: If you plan to use openrc, but openrc has not yet booted
+ the machine, you can use
+ --with-cgroup-controller=openrc
+ to let elogind know that openrc will be the controller
+ in charge.
+
+However, if you set the controller at configure time to something
+different than what is in place, elogind will not start until that
+controller is actively used as the primary controller.
+
+License
+-------
+
+LGPLv2.1+ for all code
+
+ - except src/shared/MurmurHash2.c which is Public Domain
+ - except src/shared/siphash24.c which is CC0 Public Domain
+ - except src/journal/lookup3.c which is Public Domain
+
+Dependencies
+------------
+
+ glibc >= 2.14
+ libcap
+ libmount >= 2.20 (from util-linux)
+ libseccomp >= 1.0.0 (optional)
+ libblkid >= 2.24 (from util-linux) (optional)
+ PAM >= 1.1.2 (optional)
+ libacl (optional)
+ libselinux (optional)
+ make, gcc, and similar tools
+
+During runtime, you need the following additional dependencies:
+
+ dbus >= 1.4.0 (strictly speaking optional, but recommended)
+ PolicyKit (optional)
+
+When building from git, you need the following additional
+dependencies:
+
+ pkg-config
+ docbook-xsl
+ xsltproc
+ automake
+ autoconf
+ libtool
+ intltool
+ gperf
+ gtkdocize (optional)